Washington — Amid all the controversy over President Obama's cabinet picks, it's been hard not to notice that the face of Republican opposition has lately seemed to be embodied more and more by one man in particular: South Carolina Sen. Lindsey Graham.

Senator Graham has been one of the administration's most vocal critics on the Benghazi matter, helping torpedo UN Ambassador Susan Rice's chances to become secretary of State as a near-ubiquitous presence on cable news and the Sunday shows. Just this week, he suggested he might place a hold on the nomination of John Brennan for CIA director until the administration stops what he calls its "stonewalling" on the matter.

Graham is also among those leading the charge against the nomination of former Nebraska Sen. Chuck Hagel for Defense secretary, calling it an "in your face" pick, and "incredibly controversial." He reluctantly voted for the recent "fiscal cliff" deal, but has vowed to oppose raising the debt ceiling next month unless Congress agrees to significant entitlement reforms. He says he will oppose any efforts to pass a new assault-weapons ban.

None of this would be particularly eyebrow-raising – except that in many ways it's a sharp change of direction for Graham. Like his closest Senate ally, Arizona Sen. John McCain, Graham was until fairly recently most often seen as one of those "independent" Republicans who could give his own party more trouble than the opposition. As recently as 2010, a profile in The New York Times magazine described Graham as "contentedly discussing the various fellow South Carolina conservatives who dislike him – Tea Partiers, Constitutionalists, immigration hardliners," and noted that he had apparently logged more White House visits than any other Republican senator (other than, perhaps, Maine's Susan Collins).

He also received the lowest rating of all Republican senators from the anti-tax Club for Growth – whose president, Chris Chocola, suggested at a Monitor breakfast in September that they may support a primary challenge against Graham when he goes up for reelection in 2014.

Which may help explain Graham's recent morphing into the Obama administration's antagonist in chief. If anything, Graham seems to be taking a page out of the playbook of Utah Sen. Orrin Hatch, who was initially a top target for tea party groups in 2012, but wound up winning reelection easily after a full-court press to win back support from the right.

Last month, political scientist Jordan Ragusa of the College of Charleston charted Graham's move to the right during his time in the Senate on the blog Rule22, writing: "I suspect this movement is especially pronounced in the current Senate (we don’t have the data yet) and will only accelerate in the coming 113th." He added: "the reality is that Graham has carefully prepared for a conservative challenge in 2014."

And so far, it seems to be working. A Public Policy Polling survey last month found that Graham had significantly improved his standing among Republican voters in South Carolina, going from just 37 percent saying they'd support him in a primary back in 2011 to 66 percent saying they'd support him now.